The present invention relates to the general field of applying heat treatment to preforms of parts that are made by shaping powders. The invention applies more particularly, but not exclusively, to sintering preforms of three-dimensional parts that are obtained by shaping metal or ceramic powder.
It is nowadays common practice to use methods of fabricating three-dimensional parts out of metal (or metal alloy) or out of ceramic that involve a step of shaping a powder in order to obtain a preform (e.g. by using a powder or metal injection molding (PIM or MIM) technique with the help of a binder, e.g. an organic binder, or powder compaction molding), followed by a step of sintering the preform.
During the step of sintering the preform (or of applying heat treatment at high temperature), several thermomechanical phenomena occur:                the material expands thermally, depending on the coefficient of thermal expansion of the material constituting the preform;        the shrinkage due to the powder densifying during sintering (which may represent the preform contracting by about 15% in all directions), which depends on the initial density of the powder and on sintering parameters (e.g.: temperature, pressure, duration, final density desired for the part); and        the part creeping or sagging under its own weight when the part presents a portion that is suspended (or, in other words, that is cantilevered-out).        
With complex shapes, parts may present large cantilevered-out areas that sag during the sintering step of the preform if they are not completely rigid, and this should be avoided.
Document FR 2 944 721 discloses a method of fabricating a metal part by metal powder injection molding, in which:                a mechanical support is made from a mixture of powder and binder shaped so as to support the blank along a contact surface;        the blank is arranged on the mechanical support along the contact surface; and        the assembly formed by the blank on the mechanical support is sintered simultaneously. The method described in that document serves to avoid creep in a part that presents a suspended surface. Nevertheless, the mechanical support described in that document can be used only once, since it is sintered at the same time as the part in order to accompany it and support it throughout the sintering step. The use of such a support increases considerably the quantity of powder that is needed, the cost, and the time for fabricating each part.        